i'd like a service that doesn't make me upload anything elsewhere, but serves the data directly from my computer. and only uses a server to help the sender and receiver find each other and potentially bridge the connection if a direct connection doesn't work.

bittorrent does that, but it is to much effort to create and share a torrent. i'd like to click or run a script "share this.file" and get back an URL with a key, which i can share by email. then the recipient clicks that link and downloads the file without needing any software except a standard browser.